I recently had the pleasure of finally going full Stage II after months of waiting and driving my car with wanna-be Stage II parts installed (HFC and intake). I'll start by saying that Stage II is incredible and is still surprising me with how much power my car has on tap. Every gear has torque for days (maybe not gears 7 & 8), and it pulls so strong completely through the power band. I've been able to race a couple of cars for comparison's sake with interesting results, but I'll get to that later.
So the power is great, but how about daily driving? Well, when not on the power maybe about half-throttle the driving characteristics are no different than stock. No surging or hesitations, just smooth sailing. When at about 3/4 throttle, it seems that the ECU isn't sure weather to give you full boost or not, which feels like a slight surge then release (happens in less than a second). Still not very noticeable and is easy to avoid once you know where in the throttle range it occurs.
Gas mileage is actually the same as stock if not slightly better! Now, that statement is heavily dependant on if you driving the car the same as you would with your car in stock form. Believe me, the first two weeks with the software did not help the environment whatsoever! Driving WOT almost everywhere was only getting me 240-260 miles per tank. After the romance settled and I dialed it back, I realized my mileage hadn't changed at all. I even "tried" driving much more conservatively to see if I could get a tank to 300 miles. No such luck. I had a hunch that my intake was robbing some of my MPG's so I swapped back to stock to compare and noticed a significant increase. I am now averaging 360 miles with my normal driving cycle, being aggressive when the time calls and cruising at others. I even achieved over 420 miles out of my tank on mostly HWY trip from Tampa to Melbourne and back, mostly cruising but still finding some areas to open it up.
If there is one area that I will complain, it would be the smell. I am fully aware that having a high-flow catalytic converter that is probably as efficient at cleaning my exhaust gases as a tube sock would lead to a more noticeable smell. However, it is not the smell outside of the car that I am noticing. I can fully deal with a smelly tail pipe if I am standing behind my car when at idle, which is slim to never. My issue is I can actually smell it when inside the car and driving at interstate speeds. I'm talking windows up, sunroof closed, AC on recirc. mode, passenger compartment sealed shut! I've done my due diligence and tried diagnosing any possible leak to no avail. My cat (which is the only modification to the exhaust system) is not leaking on either end. My recirc door which is clearly visible with the hood open is closed and sealed properly. I've even accessed the flow-through flaps in the rear of the car (the two sealing flaps on the rear corner of most cars, found behind our trunk access panels) and duct-taped them off. My theory was that when driving, the exhaust gases were whirling around the rear bumper area and making their way into the trunk via the flow-through flaps, hence taping them closed. But after driving the car since, I can still smell the fumes.
I actually think that the smell doesn't have anything to do with the HFC or the software for the following reason. The fact is that there are exhaust gasses entering the cabin. HFC or not, this should not be happening when the car is sealed off (windows up and recirc on). Even with a stock cat, there are still gasses exiting the tailpipe, so in my case, I would still have some form of "5-gas" entering my car. I will continue playing with it and see if I can get something sealed off so I won't have to keep driving around with my sunroof vented (sucks the gases out of the cabin). Oddly enough, I can smell them a lot more up near the headliner than down lower, my GF is 5'3'' and never smells it!
So if any other Stage II owners have any advise or opinions to the smell (interior), I am all ears!
Back to the power! I have a co-worker with an A5 that had his STG I installed the same day as my STG II, so naturally, we raced. I have a pretty solid race setup that I use to get accurate comparison results, as follows. First, I call my opponent using my Bluetooth for safe, hands-free talking as to not distract me from anything. We then enter the highway and wait for a safe gap in traffic. Once we have some room to run, we both shift into the same gear for a start @ around 50mph. Keep in mind that this is a roll-on, so Auto's need to use Tiptronic to avoid the Kickdown function. Once you're both in the same gear/speed the countdown begins and you roll away. In my case, we raced 4 times with identical results. My A4 pulled about 2 car lengths from 50-100ish, which surprised both of us. Luckily, he had some friends with G35/G37's and beat them pretty handily, restoring his confidence!
My next race came in the form of an E46 M3 with at least an exhaust modification. He was a stranger I found on the way home so I'm not sure what he had modified, but def aftermarket muffler and lowered. Either way, we accomplished a running start from 45 up through 100 and he was not able to pull on me in the slightest! I think I might have embarrassed him in front of his lady because he was very opposed to the idea of repeating the run, apparent in his actions of catching up with traffic and not letting me get beside him! I am very confident that my car would have had a huge advantage off the line up to the higher speeds but our cars seem to run out of that furious torquey feel by the 100 mph mark, so I think he would have had the top speed advantage. Either way, I was very satisfied that my car was neck and neck with an M car!
Oh, and I also ruined a $140k+ Maserati from a launch..... no big deal!
All in all, I am loving every second in my car and can't picture driving without it. Anyone that is on the fence of "Is it worth it?", the answer is hands-down yes! The sooner you save up and get it installed, the sooner you will be thanking yourself on a daily basis for this relatively inexpensive upgrade! We should also be thankful, as other cars can require you to spend thousands of dollars to get results less than ours, whereas Audi and our amazing network of tuners have given us potent engines and tuning programs that allow us to turn our relatively mild A4's into some very surprising machines!
Thank you to those who have spent your afternoon reading this and please feel free to comment and compare!
Cheers and safe motoring!
** Dave and Hugo (Stiglitz)
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I had my stage 2+ done at eurocode and I can tell you that these guys are awesome. Im just saving up to get there intercooler and then I can really be in business 
Originally Posted by Dasquade
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